Dry run all the test files together before initiating mutations

[tarunbhm]

Currently Necessist dry runs each test file and then starts mutating it line by line to find surviving mutations. The dry run of the next file required an additional build after reverting the last mutation of the earlier file. We can try to improve performance by dry running all the files together at the start, which will allow us to skip the build of the original code again and again with a dry run of every test file.

However, there is a challenge with this approach. The Necessist is built with two goals:

1. Provide useful information when something fails.
2. Be able to keep going when something fails.

Therefore to be able to find which test file had a failing test case will require parsing logic for test output for all supported frameworks. We are keeping this issue for future if we can find a better approach to handle this case.